package com.ggs.web.servlet;

import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.ByteArrayOutputStream;
import java.io.IOException;

/**
 * @author Not Today
 * @date 2019/8/5-18:54
 */
public class CheckCodeServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;

    private static int WIDTH = 70; //验证码图片宽度
    private static int HEIGHT = 20; //验证码图片高度

    public void service(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        HttpSession session = request.getSession();
        response.setContentType("image/jpeg");
        ServletOutputStream sos = response.getOutputStream();
        //设置浏览器不要缓存此图片
        response.setHeader("Pragma","No-cache");
        response.setHeader("Cache-Control","no-cache");
        response.setDateHeader("Expires", 0);
        //创建内存图象并获得其图形上下文
        BufferedImage image =
                new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_RGB);
        Graphics g = image.getGraphics();
        //产生随机的认证码
        char [] rands = generateCheckCode();
        //产生图像
        drawBackground(g);
        drawRands(g,rands);
        //结束图像的绘制过程，完成图像
        g.dispose();
        //将图像输出到客户端
        ByteArrayOutputStream bos = new ByteArrayOutputStream();
        ImageIO.write(image, "JPEG", bos);
        byte [] buf = bos.toByteArray();
        response.setContentLength(buf.length);
        //下面的语句也可写成：bos.writeTo(sos);
        sos.write(buf);
        bos.close();
        sos.close();
        //将当前验证码存入到Session中
        session.setAttribute("check_code",new String(rands));
//        System.out.println(new String(rands));
    }

    //生成一个4字符的验证码
    private char [] generateCheckCode()
    {
        //定义验证码的字符表
        String chars = "0123456789abcdefghijklmnopqrstuvwxyz";
        char [] rands = new char[4];
        for(int i=0; i<4; i++)
        {
            int rand = (int)(Math.random() * 36);
            rands[i] = chars.charAt(rand);
        }
        return rands;
    }
    private void drawRands(Graphics g , char [] rands)
    {
        g.setColor(Color.BLACK);
        g.setFont(new Font(null,Font.ITALIC|Font.BOLD,18));
        //在不同的高度上输出验证码的每个字符
        g.drawString("" + rands[0],1,17);
        g.drawString("" + rands[1],16,15);
        g.drawString("" + rands[2],31,18);
        g.drawString("" + rands[3],46,16);
//        System.out.println(rands);
    }
    private void drawBackground(Graphics g)
    {
        //画背景
        g.setColor(new Color(0xDCDCDC));
        g.fillRect(0, 0, WIDTH, HEIGHT);
        //随机产生120个干扰点
        for(int i=0; i<120; i++)
        {
            int x = (int)(Math.random() * WIDTH);
            int y = (int)(Math.random() * HEIGHT);
            int red = (int)(Math.random() * 255);
            int green = (int)(Math.random() * 255);
            int blue = (int)(Math.random() * 255);
            g.setColor(new Color(red,green,blue));
            g.drawOval(x,y,1,0);
        }
    }

}